Ruby 1.9.3 Serialport未定义的方法`start_with？

在从sp.getc更改为sp.gets后，以下脚本工作正常

require "rubygems"  
require "serialport"  
require "data_mapper"

 #params for serial port  
 port_str = "/dev/ttyACM0" 
 baud_rate = 19200  
 data_bits = 8  
 stop_bits = 1  
 parity = SerialPort::NONE  

 sp = SerialPort.new(port_str, baud_rate, data_bits, stop_bits, parity)

 loop do
   sp_char = sp.gets
   if sp_char.start_with?("Time")
     printf("%s", sp_char)
   end
 end  

然后我在Arduino中重新加载了以下内容（我认为这就是我所拥有的？）

---

似乎与Arduino或我的虚拟Debian机器有关。在重新启动虚拟机并关闭Arduino电源后，我已经启动了它

//SMS Send and Receive program
//Using Mega 2560 & Elecrow SIM900 GSM Shield
//4 July 2013

int count = 0;
int sendCount=0;
int n_sms,x,sms_start;
char data[300];

void setup()
{
Serial1.begin(19200);               // the GPRS/GSM baud rate
Serial.begin(19200);                 // the USB baud rate

Serial1.println("AT\r");
Serial1.flush();
delay(1000);
Serial1.println("AT+CMGF=1\r");
Serial1.flush();
delay(1000);
Serial.println("Text Mode Selected");
Serial.flush();
//sendSMS();
}

void loop()
{

  if(sendCount>720) //approx 60 minutes between sends
  {
    //sendSMS();
    sendCount=0;
  }
  else

    Serial1.print("AT+CMGR=1\r");    //Reads the first SMS
        Serial1.flush();
        for (x=0;x < 255;x++){
            data[x]='\0';
        }
        x=0;
        do{
            while(Serial1.available()==0);
            data[x]=Serial1.read();
            x++;
            if(data[x-1]==0x0D&&data[x-2]=='"'){
                x=0;
            }
            }while(!(data[x-1]=='K'&&data[x-2]=='O'));

        data[x-3]='\0';        //finish the string before the OK

        Serial.println(data);    //shows the message
        Serial.flush();
        Serial1.print("AT+CMGD=1,4\r");
        Serial1.flush();

        delay(5000);
        sendCount++;

}

void sendSMS()
{
Serial1.println("AT+CMGS=\"+64xxxxxxxxxx\"\r");    
//Replace this number with the target mobile number.
Serial1.flush();
delay(1000);
Serial1.println("SA\r");   //The text for the message
Serial1.flush();
delay(1000);
Serial1.write(0x1A);  //Equivalent to sending Ctrl+Z
}

irb(main):003:0> 'AT'.start_with? 'Time'
=> false
irb(main):004:0> 'Time:0902'.start_with? 'Time'
=> true